Glycoprotein D (gD) is an essential envelope protein from the herpes. simplex virus (HSV). The strains HSV-1 and HSV-2 both contain gD, and gD-1 and gD-2 are 800/6 homologous in sequence. Truncated versions of the two proteins have been cloned in a baculovirus expression system. These proteins have all the amino acids necessary for function as shown by in vitro assays, have the proper conformation, and are soluble. since they are truncated at amino acid 306 prior to the hydrophobic transmembrane region. They are called gD-1(306t) and gD-2(306t). Two additional mutants of gD-1(306t) have.been cloned and expressed. Whereas the wild-type has three N-linked carbohydrates, gD-I(TAAt) has only one and gD I (QAAt) has none. Both proteins have the -proper conformation and function in in vitro assays. The protein gD-1(306t) appears dimeric by gel filtration data. Mass analysis in the STEM agrees with this and additional measurements on all four of these protems indicate they are all dimers. The HSV glycoproteins H and L are found in the virus envelope as a hetero-oligomer. The purified gH/gL complex is being analyzed in the STEM to determine its molecular weight and to see if any structural details can be observed. The gl) (dimer)/HSV receptor complex is also going to be studied using the STEM.